/Engine/Plugins/Online/OnlineSubsystemUtils/Source/OnlineSubsystemUtils/Public/PartyBeaconHost.h
Get a count of all players for a given platform
number of players for a given platform
virtual int32 GetReservationPlatformCount ( const [FString](API\Runtime\Core\Containers\FString) & InPlatform, bool bIncludeMappedPlatforms ) const